private static Location GetOrCreateLocation(string locationName, ChainOfSupermarketsContext db)
        {
            var location = db.Locations.FirstOrDefault(l => l.Name == locationName);
            if (location == null)
            {
                location = new Location { Name = locationName };
                db.Locations.Add(location);
                db.SaveChanges();
            }

            return location;
        }
        private Location GetOrCreateLocation(string locationName)
        {
            var location = this.db.Locations.FirstOrDefault(l => l.Name == locationName);
            if (location == null)
            {
                location = new Location { Name = locationName };
                this.db.Locations.Add(location);
                this.db.SaveChanges();
            }

            return location;
        }